/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.language;

import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringEncoder;


/**
 * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
 * general purpose scheme to find word with similar phonemes.
 * 
 * @author Apache Software Foundation
 * @version $Id: Soundex.java 794026 2009-07-14 19:21:23Z ggregory $
 */
public class Soundex implements StringEncoder {

/**
 * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
 * means do not encode.
 * <p>
 * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
 * up the value for the constant values page.)
 * </p>
 * 
 * @see #US_ENGLISH_MAPPING
 */
public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";

/**
 * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
 * means do not encode.
 * 
 * @see com.mlizhi.base.codec.language.Soundex#Soundex(char[])
 */
public static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();

/**
 * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
 * 
 * @see #US_ENGLISH_MAPPING
 */
public static final Soundex US_ENGLISH = new Soundex();


/**
 * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
 * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
 * identical values.
 * 
 * @param s1
 *  A String that will be encoded and compared.
 * @param s2
 *  A String that will be encoded and compared.
 * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
 * 
 * @see SoundexUtils#difference(StringEncoder,String,String)
 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
 *  T-SQL DIFFERENCE </a>
 * 
 * @throws EncoderException
 *  if an error occurs encoding one of the strings
 * @since 1.3
 */
public int difference(String s1, String s2) throws EncoderException {
return SoundexUtils.difference(this, s1, s2);
}

/**
 * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
 * 
 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
 */
private int maxLength = 4;

/**
 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
 * letter is mapped. This implementation contains a default map for US_ENGLISH
 */
private final char[] soundexMapping;

/**
 * Creates an instance using US_ENGLISH_MAPPING
 * 
 * @see com.mlizhi.base.codec.language.Soundex#Soundex(char[])
 * @see com.mlizhi.base.codec.language.Soundex#US_ENGLISH_MAPPING
 */
public Soundex() {
this.soundexMapping = US_ENGLISH_MAPPING;
}

/**
 * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
 * mapping for a non-Western character set.
 * 
 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
 * letter is mapped. This implementation contains a default map for US_ENGLISH
 * 
 * @param mapping
 *  Mapping array to use when finding the corresponding code for a given character
 */
public Soundex(char[] mapping) {
this.soundexMapping = new char[mapping.length];
System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
}

/**
 * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
 * and/or possibly provide an internationalized mapping for a non-Western character set.
 * 
 * @param mapping
 *Mapping string to use when finding the corresponding code for a given character
 * @since 1.4
 */
public Soundex(String mapping) {
this.soundexMapping = mapping.toCharArray();
}

/**
 * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
 * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String.
 * 
 * @param pObject
 *  Object to encode
 * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
 * supplied.
 * @throws EncoderException
 *  if the parameter supplied is not of type java.lang.String
 * @throws IllegalArgumentException
 *  if a character is not mapped
 */
public Object encode(Object pObject) throws EncoderException {
if (!(pObject instanceof String)) {
throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
}
return soundex((String) pObject);
}

/**
 * Encodes a String using the soundex algorithm.
 * 
 * @param pString
 *  A String object to encode
 * @return A Soundex code corresponding to the String supplied
 * @throws IllegalArgumentException
 *  if a character is not mapped
 */
public String encode(String pString) {
return soundex(pString);
}

/**
 * Used internally by the SoundEx algorithm.
 * 
 * Consonants from the same code group separated by W or H are treated as one.
 * 
 * @param str
 *  the cleaned working string to encode (in upper case).
 * @param index
 *  the character position to encode
 * @return Mapping code for a particular character
 * @throws IllegalArgumentException
 *  if the character is not mapped
 */
private char getMappingCode(String str, int index) {
// map() throws IllegalArgumentException
char mappedChar = this.map(str.charAt(index));
// HW rule check
if (index > 1 && mappedChar != '0') {
char hwChar = str.charAt(index - 1);
if ('H' == hwChar || 'W' == hwChar) {
char preHWChar = str.charAt(index - 2);
char firstCode = this.map(preHWChar);
if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
return 0;
}
}
}
return mappedChar;
}

/**
 * Returns the maxLength. Standard Soundex
 * 
 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
 * @return int
 */
public int getMaxLength() {
return this.maxLength;
}

/**
 * Returns the soundex mapping.
 * 
 * @return soundexMapping.
 */
private char[] getSoundexMapping() {
return this.soundexMapping;
}

/**
 * Maps the given upper-case character to its Soundex code.
 * 
 * @param ch
 *  An upper-case character.
 * @return A Soundex code.
 * @throws IllegalArgumentException
 *  Thrown if <code>ch</code> is not mapped.
 */
private char map(char ch) {
int index = ch - 'A';
if (index < 0 || index >= this.getSoundexMapping().length) {
throw new IllegalArgumentException("The character is not mapped: " + ch);
}
return this.getSoundexMapping()[index];
}

/**
 * Sets the maxLength.
 * 
 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
 * @param maxLength
 *  The maxLength to set
 */
public void setMaxLength(int maxLength) {
this.maxLength = maxLength;
}

/**
 * Retrieves the Soundex code for a given String object.
 * 
 * @param str
 *  String to encode using the Soundex algorithm
 * @return A soundex code for the String supplied
 * @throws IllegalArgumentException
 *  if a character is not mapped
 */
public String soundex(String str) {
if (str == null) {
return null;
}
str = SoundexUtils.clean(str);
if (str.length() == 0) {
return str;
}
char out[] = {'0', '0', '0', '0'};
char last, mapped;
int incount = 1, count = 1;
out[0] = str.charAt(0);
// getMappingCode() throws IllegalArgumentException
last = getMappingCode(str, 0);
while ((incount < str.length()) && (count < out.length)) {
mapped = getMappingCode(str, incount++);
if (mapped != 0) {
if ((mapped != '0') && (mapped != last)) {
out[count++] = mapped;
}
last = mapped;
}
}
return new String(out);
}

}
